The effect of the addition of 5 and 10 phr of unsaturated polyester resin (UPE) on the compatibility and physicomechanical properties of Styrene-butadiene (SBR) and acrylonitrile-butadiene (NBR) rubber blends was studied. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), electrical, and ultrasonic techniques were used to determine the degree of the compatibility (DC). The results obtained revealed that, by the addition of 10 parts per hundred parts of rubber (phr) UPE as a compatibilizer for SBR/NBR blends, the degree of compatibility was greatly enhanced. The rheological and mechanical properties of the blends were also improved.